From the viewpoint of safety, sanitation and work efficiency, vehicles are used within pipes of various piping systems such as oil cargo pipes for oil tankers, and water supply pipes, sewers and gas pipes under the ground or above the ground for performing work, for example, for cleaning or coating the inner surface of the pipe. For instance, pipes are cleaned by placing into the pipe a vehicle carrying a cleaning spray device and moving the vehicle axially of the pipe. Pipes are coated similarly using a vehicle having a coating spray device mounted thereon.
However, since conventional vehicles are not of the self-propelled type, the vehicle must be moved by pulling a rope attached to the vehicle. Accordingly, when work is to be performed within a pipe using the conventional vehicle, a worker must enter the pipe first to extend and deliver the rope to another worker outside the pipe. With piping systems, the interior of which is not accessible, it is therefore necessary to remove the unit pipe to be worked on from the system at flange joints or the like, perform work in the pipe using the vehicle outside the piping system and connect the pipe to the system again after the completion of the work. The vehicle therefore has the drawback of necessitating a very cumbersome procedure on a large scale.
Furthermore, conventional vehicles are designed specifically for particular work. Cleaning vehicles are used only for cleaning, while coating vehicles are adapted to conduct a coating operation only. Accordingly, when different kinds of work are to be performed for one pipe, for example, when the pipe is to be cleaned and then coated, different vehicles need to be used for the different kinds of work. The coating operation to be conducted after the cleaning operation requires removal of the cleaning vehicle from the interior of the pipe, placement of the coating vehicle into the pipe and provision of the pulling rope, hence the problem of necessitating much time and labor.